Cob cutter blade and method of manufacture

ABSTRACT

A new and unique construction for a corn cob cutter knife is presented. A method is described for the manufacture of a unique cutting blade insert which is tapered and which has an inner ski angle compatible with the many applications involved in removing corn kernels from a corn cob in a mechanized operation. The unique removable cutting blade insert is designed so that the various angles of declination and attack optimize the sharpness and long lasting nature of the knife. A method is also presented to determine the off-set grinding radius for the ski angle of the knife.

BACKGROUND OF THE INVENTION

This invention is a continuation-in-part of patent Ser. No. 580,166,filed Sep. 10, 1990, now U.S. Pat. No. 5,195,929.

This invention relates to the field of harvester devices, and moreparticularly to the field of corn cob cutters.

The shucking of corn kernels from corn cobs has been done for over athousand years. Improvements in the field take place rapidly, the mostimportant improvement being the mechanization of the shucking procedure.Since corn cobs are grown in non-uniform sizes, the art of removing thekernels, while not removing an excessive amount of the corn cob itself,has been the object of much research and development.

The standard corn cutting machine has been well known in the art sincethe early 1930's. A common corn cutting machine now in service is shownand described in U.S. Pat. No. 2,787,273, issued to C. E. Kerr in 1957.FIG. 7 of the Kerr patent shows the corn cob cutting knife manufacturedas one piece. A new and improved design for the knife is the currentsubject of this patent. This improved design is basically of two-partconstruction, having a base and a cutting blade insert. The instantcutting blade insert is unique in that the blade insert improves thecorn cob cutting performance by changing the position of the knifesurface that rides on the cob.

Many cutter knives are in common use throughout the trade and theirshape is largely determined by the machines currently in use in theagricultural harvesting of corn. This invention particularly relates tothe knife as shown generally in the Kerr Patent, FIG. 7.

Much attention has been drawn to the manufacture of a suitable knife.The sharpness of the knife, as well as the length of service time hasbeen a main object of exploration in this field. Additionally, becausecorn cobs come in various sizes and are usually tapered within theindividual cob itself, there has been a long felt need to develop aknife which will suitably remove the kernels of corn from the cob whilenot also cutting the cob itself. Cutting the cob itself during theharvesting of corn kernels not only adds unwanted material to the kernelproduct, it also tends to dull the knife thus requiring frequentsharpening or complete substitution of the knife.

One approach to the problem of dulling the knives is described in the1989 U.S. patent issued to Maruska, U.S. Pat. No. 4,802,495. The Maruskapatent directed itself to a method and apparatus for renewing cuttingedges in corn processing equipment by providing a replaceable blade forthe cutting knife. The replaceable blade is held in place by means of ascrew and shoe. The shoe is shown and described in FIG. 11 of the '495patent. However, both Kerr and Maruska fail to solve the problem ofrapid dulling of the blade cutting edge or the cutting edge chipping orbreaking. The point of the cutting edge cuts the most corn and isdamaged or dulled first.

It is an object of this invention to provide a new cob cutting bladewhich has the added feature of reducing the knife point digging into thecob, therefore increasing blade cutting life. In taking into account thedifferent dimensions of corn ears, a method is described by which aprecise radius and angle of taper of the knife are determined so thatthe optimum attack angles for the knife are produced.

It is also an object of this invention to provide a unique andreplaceable cutting blade insert designed so that cutting into the cobitself during the shucking procedure is reduced. It is a further objectof this invention to provide a new cob cutting blade insert that willlast longer and stay sharper than the conventional knives now in use. Itis further an object of this invention to provide a cob cutting bladeinsert that may be made of high quality steel and yet is economical tomanufacture and use in the cob cutting process.

Other and further objects of this invention will become obvious uponreading the following Specification.

BRIEF DESCRIPTION OF THE INVENTION

A cob cutting blade for a cob cutter knife is manufactured using amethod which not only describes the manufacture of the actual bladeitself, but also provides a method for determining the off-set grindingradius for the ski angle surface.

A three step method describes the manufacture of the knife blade insert.The knife blank has a twenty-five degree angle cut across the upper edgeof the blade. The blade itself has a curved cross-section. The inner skisurface is then machined so that an inner off-set, non-concentricsurface is produced. The outer surface is then ground in the final stepto produce a cutting angle of approximately 8.6 degrees relative to thecob. The 8.6 degree cross sectional cutting angle has been determined tobe of an optimum angle for removing corn kernels from a cob.

Since the inner and outer surfaces are machined off-set from themounting center of the blade, the surfaces of the blade are notconcentric. The leading edge of the blade is slightly off-set from thecob surface, resulting in detection of a hard cob surface. A seven stepprocedure determines the off-set grinding radius for the ski angle. Thisprocedure results in the optimum shape for a blade for removing kernelsof corn from various size and geometrically shaped corn cobs.

A new square knife control piece is also provided so as to reduce wearon the knife blade as it pivots about its knife pivot point. This newpiece comprises a square bushing which contacts the square knife controlslot on the standard knife blade. Inside this bushing is a circularpivot pin which is connected to the standard cob knife drivingmechanism.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a perspective view of the knife and cutting blade insert.

FIG. 2 is a top plan view of the holder and cutting blade insert withthe top part of the blade holder in cross section, taken along Lines2--2 of FIG. 1.

FIG. 3 is a side view of the cutting blade showing the shape of theblade in its initial stages, with an arrow showing the direction ofrotation of the blade around the cob.

FIG. 4 is a cross sectional view of the cutting blade insert showing,the inside ski angle.

FIG. 5 is an end view of the cutting blade insert showing the off-setradius for the inside ski angle, with an arrow showing the direction ofrotation of the blade around the cob.

FIG. 6 shows the various measurements used to determine the off-setgrinding radius of the inside ski angle.

FIG. 7 is an exploded view of the end of the cutting blade insert andthe cutting blade insert holder.

FIG. 8 is an end view of the cutting blade insert knife edge, takenalong lines 8--8 of FIG. 7.

FIG. 9 is a partial cutaway view showing the knife in its environment ofuse in the standard cob cutting machine.

FIG. 10 is a top view of the knife control unit showing the squarecontrol unit and bushing.

FIG. 11 is a side view of the pivot pin used to move the knife blade.

FIG. 12 is an exploded top view of the blade insert and holder showingthe tapered-groove holder.

DESCRIPTION OF THE PREFERRED EMBODIMENT

A cob cutter knife 1 comprises generally a base having a counterweightportion 2, a shank portion 3 and a cutting blade insert 4. The removablecutting blade insert 4 is inserted into opposite tapered grooves 5(shown on FIG. 12) and is locked into position by the set screw 6. Thegrooves are tapered at an eight (8) degree angle, as shown on FIG. 12.The set screw is preferably of the Allen type and may tighten thecutting blade insert 4 so that it is fixedly secured in place by thetension between the screw 6, the blade and the tapered grooves 5. Ablade holder 7 is formed with the counterweight portion 2 and the shankportion 3 in a unitary fashion. The blade holder 7 and cutting bladeinsert 4 pivot about a point 8. The blade holder and cutting bladeinsert with their mountings rotate, as shown and described in the KerrPatent. The knife 1 is placed in its environment of use as best shown onFIG. 9.

Many problems are encountered in the cob cutting trade due to theimperfections in determining the shape of the cutting blade insert andof the cutting angles which are required to optimize the efficiency ofthe cutting edge. The improved cutting blade insert as shown herein isproduced by a unique three step method illustrated in FIGS. 3 through 5.

FIG. 3 shows the side view of the cutting blade insert 4. The removablecutting blade insert 4 has a mounting base 10 and an upper cuttingportion 11. The blade is secured when the set-screw 6 is tightenedagainst the set-screw seat 9. The ideal over-all length of the cuttingblade insert is approximately 1.25 inches before resharpening. As shownon FIG. 3, the blade cutting edge 26 of the upper cutting portion 11 ofthe blade is tapered inwardly at an angle of approximately twenty-fivedegrees as shown. It has been found that this angle of taper should bebetween 23 degrees and 27 degrees. The lower point 31 does not cut cornunless the cob is very large. In the preparation of a cutting bladeinsert, it is very important to determine an inner ski angle for theinner surface of the blade which rides on the cob.

FIG. 4 describes the second step in the procedure for producing aproperly dimensioned cutting blade for corn kernel removal.

The blade insert 4 has a curvilinear rectangular cross section, as shownon FIG. 12. It is necessary to cut a ski angle in this cross sectionwhich creates an inner surface 28 as shown on FIGS. 4 and 8. As bestshown on FIG. 4, the cutting blade insert 4 is machined so as to createa ski angle 12 on the inner surface of the blade insert. This machiningis accomplished by determining an off-set dimension. Using this off-setdimension, the centerline of the blade insert is off-set from thecenterline of the cob and non-concentric off-set surfaces are produced.It has been found that this ski angle 12 operates well at approximately1.8 degrees. (The drawing shows 6.8 degrees due to 5 degrees on theholder.)

In the optimum range, the ski radius for the cutting edge, as shown onFIG. 5 is 0.79 inches. In order to taper the cutting edge downwardly andin a curved manner, to create the unique cutting surfaces describedherein, the actual grinding radius is off-set approximately 0.015inches. As shown on FIG. 5, an off-set grinding radius 13 is determinedby a unique formula. The center line 14 of the cutting blade insert isused to mount the blade while the off-set grinding dimension 15 is usedto cut the inside ski surface 28. During corn cutting the center of thecob is at the center line 14. Using these dimensions, the ski angle forthe cutting blade insert is completed. The offset dimension 15 forcesthe edge 16 of the ski angle to ride on the cob which holds the knifecutting edge point 17 up from the cob.

Turning now to Step 3, a final angle 18 must be ground on the outersurface 29 of the blade. This final angle 18 is approximately 10.5degrees. This angle 18 is ground into the blade insert by using a secondoff-set, the manufacturing of which is well known in the art, beingidentical to the method used in the Kerr knife. Having completed thisthree step process shown in FIGS. 3 through 5, the knife insert is nowready to be positioned within the holder of the knife itself. The secondoffset and radius is varied to obtain cutting edge 26 in FIG. 3.

The diameter of a corn cob varies a great deal due to the naturalprocesses of growing ears of corn. A corn cob will generally vary frombetween 1 inch to 13/4 inches in diameter. Since the cutter knivesthemselves are normally biased towards a 1 inch diameter, it isnecessary for a mechanism, shown and described in the Kerr and otherpatents, to bias the knives closed. This bias closed, when coupled withthe various sizes of the corn cobs, increases the probability of theknife cutting into the cob. The production of a suitable cutting bladeinsert is an important component in the production of the most efficientcob cutting device. FIG. 6 details a method for determining the mostefficient off-set dimension 15 for the ski surface 28. (See FIGS. 4 and5.

The first step in locating this off-set dimension 15 (FIG. 5) is to drawcenter lines and arrive at a point of origin 19, shown on FIG. 6. Thenext step is to draw a 0.500 radius 20 (which represents the diameterfor small cobs). This radius intersects the vertical center line atsmall cob diameter point 21. A large cob diameter point 22 is thenlocated along the vertical center line. This large corn cob diameterpoint 22 is located by drawing a 0.875 inches radius from point 21 alongthe vertical center line. The fourth point to be located in thisprocedure is the location of the knife pivot point 23. A distance havinga radius 24 of 2.625 inches from point 22 is now located along thehorizontal center line. (A sweet corn cob center is the distance frompoints 19 to 22.) The fifth step in determining the off-set radius 13 isdone by drawing a 0.790 inches radius 25 from the small cob point 21.The 0.790 inches radius 25 has been determined to be the optimum forthis procedure by past experimental usage and is in common usethroughout the industry. A final radius 27 of 2.640 inches (drawn fromexperimental tests for optimum results) is taken from the knife pivotpoint 23. The intersection 37 of radius 25 and radius 27 in the lowerright quadrant of said centerlines provides off-set 15 in FIG. 5.Off-set 15 is the distance between the intersection of arcs 25 and 27and the vertical centerline. This method stabilizes the optimum cuttingradius for the blade and is used to grind the ski surface 28. Thisprocedure provides the optimum position of the knife cutting edge tofollow the 1 inch diameter cob or the 13/4 inch diameter cob. The knifecutting edge is moving in and out for the cob diameters and thereforethe angular positions vary because the knife rotates about point 23.

The finished blade insert 4 is shown on FIGS. 7 and 8. The blade has aninner cutting surface 28 and an outer surface 29. The top edge 26 of thefinished blade shown on FIG. 8 separates the two surfaces. Due to theunique method of grinding, the inner and outer surfaces 28 and 29, andthe cutting edge 26 is offset from the cob centerline. This offsetfeature provides a longer lasting and more reliable cutting blade.

Referring back to FIGS. 1 and 9, the general configuration and shape ofthe knife 1 is shown. A number of knives, as best shown on FIG. 9, areattached in a circular fashion to form a kaleidoscope type opening 30for the insertion of an ear of corn. The knife pivots about point 8 andis controlled by a mechanism that is inserted into the arm force square32. This square 32 controls the opening and closing of the knife througha controlling mechanism. Normally, this arm force square is controlledby a circular pin 33, as shown on FIG. 9. However, it has been foundthat a circular pin controlling the knife is prone to wear and thereforeknife control is lost when used over an extended period of time. Thisphenomenon occurs because a circular pin only contacts the square forcearea at its tangential surfaces. Pivot pin 33, FIG. 9, is the point atwhich the knife is controlled. The knives are driven by pins (at point 8for each knife) which are attached to a circular plate 37. Another plate38 contains the control pins 33. As plate 38 moves counterclockwise at agreater rate than plate 37, the knives close.

In order to improve on the effectiveness and life of the controlmechanism used to control the knife shank and blade, a square pivot hasbeen developed. This unique square pivot is shown and described in FIGS.10 and 11. FIG. 10 is a top view of the square pivot. The center 34 ofthis square, shown in FIG. 10, is adapted to receive the pin 33 (FIG.11) that controls the knife opening and closing. This square pivotcontrol mechanism comprises a square base 35 and a bushing 36. The pin33 is driven by the standard driving mechanisms 38 and 39 for corn cobcutter machines in a manner that is well known in the art. The pin 33,which has a circular cross section, is inserted into the center of thesquare bushing 34 and the square bushing is forced in the normaldirection. Forcing the square bushing will pivot the knife about pivotpoint 8, thus opening or closing the knife about the corn cob.

Since our knife comprises a base and a removable blade, different typesof material may be used in the construction of the different parts ofthe knife 1. Better tool steel may now be utilized for the removableblade, thus prolonging the sharpness and standard stainless steelmaterial. However, with a cutting blade insert, a more expensive andlonger lasting type of steel material may be utilized for the smallremovable blades. With a cutting blade insert, manufacture is possiblewith the high strength tool steel or other materials. This type of steelis manufactured by the Teledyne Company. 17-4 stainless steel, which isless expensive, yet as useful, for the base, makes up that portion ofthe knife. The common types of steel in use for making other knives areA-2 steel and S-2 steel, depending on the application. In the otherapplications for the manufacture of knives a compromise between the highgrade steel needed for the cutting blade and the less expensive steelneeded for the base is necessary. In the instant case, a much highergrade steel may be used for the cutting blade since the construction isnot unitary. In addition, the manufacturing cost is less with thecutting blade insert.

It has been found that the higher grade steel used in the instantremovable cutting blade will increase the life span and sharpness of theremovable blade herein by approximately 40%. Additionally, due to theunique design and placement of the instant cutting blade, the leadingpoint of the blade does not dig into the cob and thus there is lessbreakage and other unwanted material shucked from the cob. A uniquefeature herein is that the leading point of this blade is off-setslightly from the corn cob surface thus reducing breakage and otherdamage.

Having fully described my new invention, I claim:
 1. A method formanufacturing a cutting blade insert for a corn cutter knife,comprising:(a) making a standard blade insert with a curvilinearcross-section; (b) off-setting the grinding mechanism by approximately0.015 inches; (c) grinding an outer surface, an inner ski surface and anupper cutting edge by using a grinding radius of approximately 0.79inches; whereby a cutting blade having off-set, non-concentriccontinuous curvilinear outer and inner surfaces and a top edge isproduced.
 2. The cutting blade insert manufactured by the methoddescribed in claim
 1. 3. A cutting blade insert for corn cutter knifefor cutting kernels from a cob, manufactured by the method described inclaim 1, comprising a lower blade mounting base and an upper cuttingportion having a curvilinear cross section, wherein said upper cuttingportion comprises:(a) an off-set, non-concentric outer surface; (b) anupper continuous curvilinear cutting edge having a lower leading pointand an upper knife cutting edge point wherein said upper cutting edge isoff-set and non-concentric from said lower curvilinear base portion; (c)an off-set, non-concentric continuous curvilinear inner ski surface;wherein said blade is detachably removable and replaceable by means of aset screw and tapered grooves which receive said blade insert, (d)whereby said off-set, non-concentric continuous curvilinear inner skisurface rides on the cob and holds the cutting edge up from said cob.